1 /*
   2  * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /*
  27  * This file is available under and governed by the GNU General Public
  28  * License version 2 only, as published by the Free Software Foundation.
  29  * However, the following notice accompanied the original version of this
  30  * file:
  31  *
  32  * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
  33  *
  34  * All rights reserved.
  35  *
  36  * Redistribution and use in source and binary forms, with or without
  37  * modification, are permitted provided that the following conditions are met:
  38  *
  39  *  * Redistributions of source code must retain the above copyright notice,
  40  *    this list of conditions and the following disclaimer.
  41  *
  42  *  * Redistributions in binary form must reproduce the above copyright notice,
  43  *    this list of conditions and the following disclaimer in the documentation
  44  *    and/or other materials provided with the distribution.
  45  *
  46  *  * Neither the name of JSR-310 nor the names of its contributors
  47  *    may be used to endorse or promote products derived from this software
  48  *    without specific prior written permission.
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  51  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  52  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  53  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  54  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  55  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  56  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  57  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  58  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  59  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  60  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  61  */
  62 package java.time;
  63 
  64 import static java.time.LocalTime.MINUTES_PER_HOUR;
  65 import static java.time.LocalTime.NANOS_PER_MILLI;
  66 import static java.time.LocalTime.NANOS_PER_SECOND;
  67 import static java.time.LocalTime.SECONDS_PER_DAY;
  68 import static java.time.LocalTime.SECONDS_PER_HOUR;
  69 import static java.time.LocalTime.SECONDS_PER_MINUTE;
  70 import static java.time.temporal.ChronoField.NANO_OF_SECOND;
  71 import static java.time.temporal.ChronoUnit.DAYS;
  72 import static java.time.temporal.ChronoUnit.NANOS;
  73 import static java.time.temporal.ChronoUnit.SECONDS;
  74 
  75 import java.io.DataInput;
  76 import java.io.DataOutput;
  77 import java.io.IOException;
  78 import java.io.InvalidObjectException;
  79 import java.io.ObjectInputStream;
  80 import java.io.Serializable;
  81 import java.math.BigDecimal;
  82 import java.math.BigInteger;
  83 import java.math.RoundingMode;
  84 import java.time.format.DateTimeParseException;
  85 import java.time.temporal.ChronoField;
  86 import java.time.temporal.ChronoUnit;
  87 import java.time.temporal.Temporal;
  88 import java.time.temporal.TemporalAmount;
  89 import java.time.temporal.TemporalUnit;
  90 import java.time.temporal.UnsupportedTemporalTypeException;
  91 import java.util.Arrays;
  92 import java.util.Collections;
  93 import java.util.List;
  94 import java.util.Objects;
  95 import java.util.regex.Matcher;
  96 import java.util.regex.Pattern;
  97 
  98 /**
  99  * A time-based amount of time, such as '34.5 seconds'.
 100  * <p>
 101  * This class models a quantity or amount of time in terms of seconds and nanoseconds.
 102  * It can be accessed using other duration-based units, such as minutes and hours.
 103  * In addition, the {@link ChronoUnit#DAYS DAYS} unit can be used and is treated as
 104  * exactly equal to 24 hours, thus ignoring daylight savings effects.
 105  * See {@link Period} for the date-based equivalent to this class.
 106  * <p>
 107  * A physical duration could be of infinite length.
 108  * For practicality, the duration is stored with constraints similar to {@link Instant}.
 109  * The duration uses nanosecond resolution with a maximum value of the seconds that can
 110  * be held in a {@code long}. This is greater than the current estimated age of the universe.
 111  * <p>
 112  * The range of a duration requires the storage of a number larger than a {@code long}.
 113  * To achieve this, the class stores a {@code long} representing seconds and an {@code int}
 114  * representing nanosecond-of-second, which will always be between 0 and 999,999,999.
 115  * The model is of a directed duration, meaning that the duration may be negative.
 116  * <p>
 117  * The duration is measured in "seconds", but these are not necessarily identical to
 118  * the scientific "SI second" definition based on atomic clocks.
 119  * This difference only impacts durations measured near a leap-second and should not affect
 120  * most applications.
 121  * See {@link Instant} for a discussion as to the meaning of the second and time-scales.
 122  *
 123  * <p>
 124  * This is a <a href="{@docRoot}/java/lang/doc-files/ValueBased.html">value-based</a>
 125  * class; use of identity-sensitive operations (including reference equality
 126  * ({@code ==}), identity hash code, or synchronization) on instances of
 127  * {@code Duration} may have unpredictable results and should be avoided.
 128  * The {@code equals} method should be used for comparisons.
 129  *
 130  * @implSpec
 131  * This class is immutable and thread-safe.
 132  *
 133  * @since 1.8
 134  */
 135 public final class Duration
 136         implements TemporalAmount, Comparable<Duration>, Serializable {
 137 
 138     /**
 139      * Constant for a duration of zero.
 140      */
 141     public static final Duration ZERO = new Duration(0, 0);
 142     /**
 143      * Serialization version.
 144      */
 145     private static final long serialVersionUID = 3078945930695997490L;
 146     /**
 147      * Constant for nanos per second.
 148      */
 149     private static final BigInteger BI_NANOS_PER_SECOND = BigInteger.valueOf(NANOS_PER_SECOND);
 150     /**
 151      * The pattern for parsing.
 152      */
 153     private static final Pattern PATTERN =
 154             Pattern.compile("([-+]?)P(?:([-+]?[0-9]+)D)?" +
 155                     "(T(?:([-+]?[0-9]+)H)?(?:([-+]?[0-9]+)M)?(?:([-+]?[0-9]+)(?:[.,]([0-9]{0,9}))?S)?)?",
 156                     Pattern.CASE_INSENSITIVE);
 157 
 158     /**
 159      * The number of seconds in the duration.
 160      */
 161     private final long seconds;
 162     /**
 163      * The number of nanoseconds in the duration, expressed as a fraction of the
 164      * number of seconds. This is always positive, and never exceeds 999,999,999.
 165      */
 166     private final int nanos;
 167 
 168     //-----------------------------------------------------------------------
 169     /**
 170      * Obtains a {@code Duration} representing a number of standard 24 hour days.
 171      * <p>
 172      * The seconds are calculated based on the standard definition of a day,
 173      * where each day is 86400 seconds which implies a 24 hour day.
 174      * The nanosecond in second field is set to zero.
 175      *
 176      * @param days  the number of days, positive or negative
 177      * @return a {@code Duration}, not null
 178      * @throws ArithmeticException if the input days exceeds the capacity of {@code Duration}
 179      */
 180     public static Duration ofDays(long days) {
 181         return create(Math.multiplyExact(days, SECONDS_PER_DAY), 0);
 182     }
 183 
 184     /**
 185      * Obtains a {@code Duration} representing a number of standard hours.
 186      * <p>
 187      * The seconds are calculated based on the standard definition of an hour,
 188      * where each hour is 3600 seconds.
 189      * The nanosecond in second field is set to zero.
 190      *
 191      * @param hours  the number of hours, positive or negative
 192      * @return a {@code Duration}, not null
 193      * @throws ArithmeticException if the input hours exceeds the capacity of {@code Duration}
 194      */
 195     public static Duration ofHours(long hours) {
 196         return create(Math.multiplyExact(hours, SECONDS_PER_HOUR), 0);
 197     }
 198 
 199     /**
 200      * Obtains a {@code Duration} representing a number of standard minutes.
 201      * <p>
 202      * The seconds are calculated based on the standard definition of a minute,
 203      * where each minute is 60 seconds.
 204      * The nanosecond in second field is set to zero.
 205      *
 206      * @param minutes  the number of minutes, positive or negative
 207      * @return a {@code Duration}, not null
 208      * @throws ArithmeticException if the input minutes exceeds the capacity of {@code Duration}
 209      */
 210     public static Duration ofMinutes(long minutes) {
 211         return create(Math.multiplyExact(minutes, SECONDS_PER_MINUTE), 0);
 212     }
 213 
 214     //-----------------------------------------------------------------------
 215     /**
 216      * Obtains a {@code Duration} representing a number of seconds.
 217      * <p>
 218      * The nanosecond in second field is set to zero.
 219      *
 220      * @param seconds  the number of seconds, positive or negative
 221      * @return a {@code Duration}, not null
 222      */
 223     public static Duration ofSeconds(long seconds) {
 224         return create(seconds, 0);
 225     }
 226 
 227     /**
 228      * Obtains a {@code Duration} representing a number of seconds and an
 229      * adjustment in nanoseconds.
 230      * <p>
 231      * This method allows an arbitrary number of nanoseconds to be passed in.
 232      * The factory will alter the values of the second and nanosecond in order
 233      * to ensure that the stored nanosecond is in the range 0 to 999,999,999.
 234      * For example, the following will result in the exactly the same duration:
 235      * <pre>
 236      *  Duration.ofSeconds(3, 1);
 237      *  Duration.ofSeconds(4, -999_999_999);
 238      *  Duration.ofSeconds(2, 1000_000_001);
 239      * </pre>
 240      *
 241      * @param seconds  the number of seconds, positive or negative
 242      * @param nanoAdjustment  the nanosecond adjustment to the number of seconds, positive or negative
 243      * @return a {@code Duration}, not null
 244      * @throws ArithmeticException if the adjustment causes the seconds to exceed the capacity of {@code Duration}
 245      */
 246     public static Duration ofSeconds(long seconds, long nanoAdjustment) {
 247         long secs = Math.addExact(seconds, Math.floorDiv(nanoAdjustment, NANOS_PER_SECOND));
 248         int nos = (int) Math.floorMod(nanoAdjustment, NANOS_PER_SECOND);
 249         return create(secs, nos);
 250     }
 251 
 252     //-----------------------------------------------------------------------
 253     /**
 254      * Obtains a {@code Duration} representing a number of milliseconds.
 255      * <p>
 256      * The seconds and nanoseconds are extracted from the specified milliseconds.
 257      *
 258      * @param millis  the number of milliseconds, positive or negative
 259      * @return a {@code Duration}, not null
 260      */
 261     public static Duration ofMillis(long millis) {
 262         long secs = millis / 1000;
 263         int mos = (int) (millis % 1000);
 264         if (mos < 0) {
 265             mos += 1000;
 266             secs--;
 267         }
 268         return create(secs, mos * 1000_000);
 269     }
 270 
 271     //-----------------------------------------------------------------------
 272     /**
 273      * Obtains a {@code Duration} representing a number of nanoseconds.
 274      * <p>
 275      * The seconds and nanoseconds are extracted from the specified nanoseconds.
 276      *
 277      * @param nanos  the number of nanoseconds, positive or negative
 278      * @return a {@code Duration}, not null
 279      */
 280     public static Duration ofNanos(long nanos) {
 281         long secs = nanos / NANOS_PER_SECOND;
 282         int nos = (int) (nanos % NANOS_PER_SECOND);
 283         if (nos < 0) {
 284             nos += NANOS_PER_SECOND;
 285             secs--;
 286         }
 287         return create(secs, nos);
 288     }
 289 
 290     //-----------------------------------------------------------------------
 291     /**
 292      * Obtains a {@code Duration} representing an amount in the specified unit.
 293      * <p>
 294      * The parameters represent the two parts of a phrase like '6 Hours'. For example:
 295      * <pre>
 296      *  Duration.of(3, SECONDS);
 297      *  Duration.of(465, HOURS);
 298      * </pre>
 299      * Only a subset of units are accepted by this method.
 300      * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 301      * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 302      *
 303      * @param amount  the amount of the duration, measured in terms of the unit, positive or negative
 304      * @param unit  the unit that the duration is measured in, must have an exact duration, not null
 305      * @return a {@code Duration}, not null
 306      * @throws DateTimeException if the period unit has an estimated duration
 307      * @throws ArithmeticException if a numeric overflow occurs
 308      */
 309     public static Duration of(long amount, TemporalUnit unit) {
 310         return ZERO.plus(amount, unit);
 311     }
 312 
 313     //-----------------------------------------------------------------------
 314     /**
 315      * Obtains an instance of {@code Duration} from a temporal amount.
 316      * <p>
 317      * This obtains a duration based on the specified amount.
 318      * A {@code TemporalAmount} represents an  amount of time, which may be
 319      * date-based or time-based, which this factory extracts to a duration.
 320      * <p>
 321      * The conversion loops around the set of units from the amount and uses
 322      * the {@linkplain TemporalUnit#getDuration() duration} of the unit to
 323      * calculate the total {@code Duration}.
 324      * Only a subset of units are accepted by this method. The unit must either
 325      * have an {@linkplain TemporalUnit#isDurationEstimated() exact duration}
 326      * or be {@link ChronoUnit#DAYS} which is treated as 24 hours.
 327      * If any other units are found then an exception is thrown.
 328      *
 329      * @param amount  the temporal amount to convert, not null
 330      * @return the equivalent duration, not null
 331      * @throws DateTimeException if unable to convert to a {@code Duration}
 332      * @throws ArithmeticException if numeric overflow occurs
 333      */
 334     public static Duration from(TemporalAmount amount) {
 335         Objects.requireNonNull(amount, "amount");
 336         Duration duration = ZERO;
 337         for (TemporalUnit unit : amount.getUnits()) {
 338             duration = duration.plus(amount.get(unit), unit);
 339         }
 340         return duration;
 341     }
 342 
 343     //-----------------------------------------------------------------------
 344     /**
 345      * Obtains a {@code Duration} from a text string such as {@code PnDTnHnMn.nS}.
 346      * <p>
 347      * This will parse a textual representation of a duration, including the
 348      * string produced by {@code toString()}. The formats accepted are based
 349      * on the ISO-8601 duration format {@code PnDTnHnMn.nS} with days
 350      * considered to be exactly 24 hours.
 351      * <p>
 352      * The string starts with an optional sign, denoted by the ASCII negative
 353      * or positive symbol. If negative, the whole period is negated.
 354      * The ASCII letter "P" is next in upper or lower case.
 355      * There are then four sections, each consisting of a number and a suffix.
 356      * The sections have suffixes in ASCII of "D", "H", "M" and "S" for
 357      * days, hours, minutes and seconds, accepted in upper or lower case.
 358      * The suffixes must occur in order. The ASCII letter "T" must occur before
 359      * the first occurrence, if any, of an hour, minute or second section.
 360      * At least one of the four sections must be present, and if "T" is present
 361      * there must be at least one section after the "T".
 362      * The number part of each section must consist of one or more ASCII digits.
 363      * The number may be prefixed by the ASCII negative or positive symbol.
 364      * The number of days, hours and minutes must parse to a {@code long}.
 365      * The number of seconds must parse to a {@code long} with optional fraction.
 366      * The decimal point may be either a dot or a comma.
 367      * The fractional part may have from zero to 9 digits.
 368      * <p>
 369      * The leading plus/minus sign, and negative values for other units are
 370      * not part of the ISO-8601 standard.
 371      * <p>
 372      * Examples:
 373      * <pre>
 374      *    "PT20.345S" -- parses as "20.345 seconds"
 375      *    "PT15M"     -- parses as "15 minutes" (where a minute is 60 seconds)
 376      *    "PT10H"     -- parses as "10 hours" (where an hour is 3600 seconds)
 377      *    "P2D"       -- parses as "2 days" (where a day is 24 hours or 86400 seconds)
 378      *    "P2DT3H4M"  -- parses as "2 days, 3 hours and 4 minutes"
 379      *    "PT-6H3M"    -- parses as "-6 hours and +3 minutes"
 380      *    "-PT6H3M"    -- parses as "-6 hours and -3 minutes"
 381      *    "-PT-6H+3M"  -- parses as "+6 hours and -3 minutes"
 382      * </pre>
 383      *
 384      * @param text  the text to parse, not null
 385      * @return the parsed duration, not null
 386      * @throws DateTimeParseException if the text cannot be parsed to a duration
 387      */
 388     public static Duration parse(CharSequence text) {
 389         Objects.requireNonNull(text, "text");
 390         Matcher matcher = PATTERN.matcher(text);
 391         if (matcher.matches()) {
 392             // check for letter T but no time sections
 393             if (!charMatch(text, matcher.start(3), matcher.end(3), 'T')) {
 394                 boolean negate = charMatch(text, matcher.start(1), matcher.end(1), '-');
 395 
 396                 int dayStart = matcher.start(2), dayEnd = matcher.end(2);
 397                 int hourStart = matcher.start(4), hourEnd = matcher.end(4);
 398                 int minuteStart = matcher.start(5), minuteEnd = matcher.end(5);
 399                 int secondStart = matcher.start(6), secondEnd = matcher.end(6);
 400                 int fractionStart = matcher.start(7), fractionEnd = matcher.end(7);
 401 
 402                 if (dayStart >= 0 || hourStart >= 0 || minuteStart >= 0 || secondStart >= 0) {
 403                     long daysAsSecs = parseNumber(text, dayStart, dayEnd, SECONDS_PER_DAY, "days");
 404                     long hoursAsSecs = parseNumber(text, hourStart, hourEnd, SECONDS_PER_HOUR, "hours");
 405                     long minsAsSecs = parseNumber(text, minuteStart, minuteEnd, SECONDS_PER_MINUTE, "minutes");
 406                     long seconds = parseNumber(text, secondStart, secondEnd, 1, "seconds");
 407                     boolean negativeSecs = secondStart >= 0 && text.charAt(secondStart) == '-';
 408                     int nanos = parseFraction(text, fractionStart, fractionEnd, negativeSecs ? -1 : 1);
 409                     try {
 410                         return create(negate, daysAsSecs, hoursAsSecs, minsAsSecs, seconds, nanos);
 411                     } catch (ArithmeticException ex) {
 412                         throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: overflow", text, 0).initCause(ex);
 413                     }
 414                 }
 415             }
 416         }
 417         throw new DateTimeParseException("Text cannot be parsed to a Duration", text, 0);
 418     }
 419 
 420     private static boolean charMatch(CharSequence text, int start, int end, char c) {
 421         return (start >= 0 && end == start + 1 && text.charAt(start) == c);
 422     }
 423 
 424     private static long parseNumber(CharSequence text, int start, int end, int multiplier, String errorText) {
 425         // regex limits to [-+]?[0-9]+
 426         if (start < 0 || end < 0) {
 427             return 0;
 428         }
 429         try {
 430             long val = Long.parseLong(text, start, end, 10);
 431             return Math.multiplyExact(val, multiplier);
 432         } catch (NumberFormatException | ArithmeticException ex) {
 433             throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: " + errorText, text, 0).initCause(ex);
 434         }
 435     }
 436 
 437     private static int parseFraction(CharSequence text, int start, int end, int negate) {
 438         // regex limits to [0-9]{0,9}
 439         if (start < 0 || end < 0 || end - start == 0) {
 440             return 0;
 441         }
 442         try {
 443             int fraction = Integer.parseInt(text, start, end, 10);
 444 
 445             // for number strings smaller than 9 digits, interpret as if there
 446             // were trailing zeros
 447             for (int i = end - start; i < 9; i++) {
 448                 fraction *= 10;
 449             }
 450             return fraction * negate;
 451         } catch (NumberFormatException | ArithmeticException ex) {
 452             throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: fraction", text, 0).initCause(ex);
 453         }
 454     }
 455 
 456     private static Duration create(boolean negate, long daysAsSecs, long hoursAsSecs, long minsAsSecs, long secs, int nanos) {
 457         long seconds = Math.addExact(daysAsSecs, Math.addExact(hoursAsSecs, Math.addExact(minsAsSecs, secs)));
 458         if (negate) {
 459             return ofSeconds(seconds, nanos).negated();
 460         }
 461         return ofSeconds(seconds, nanos);
 462     }
 463 
 464     //-----------------------------------------------------------------------
 465     /**
 466      * Obtains a {@code Duration} representing the duration between two temporal objects.
 467      * <p>
 468      * This calculates the duration between two temporal objects. If the objects
 469      * are of different types, then the duration is calculated based on the type
 470      * of the first object. For example, if the first argument is a {@code LocalTime}
 471      * then the second argument is converted to a {@code LocalTime}.
 472      * <p>
 473      * The specified temporal objects must support the {@link ChronoUnit#SECONDS SECONDS} unit.
 474      * For full accuracy, either the {@link ChronoUnit#NANOS NANOS} unit or the
 475      * {@link ChronoField#NANO_OF_SECOND NANO_OF_SECOND} field should be supported.
 476      * <p>
 477      * The result of this method can be a negative period if the end is before the start.
 478      * To guarantee to obtain a positive duration call {@link #abs()} on the result.
 479      *
 480      * @param startInclusive  the start instant, inclusive, not null
 481      * @param endExclusive  the end instant, exclusive, not null
 482      * @return a {@code Duration}, not null
 483      * @throws DateTimeException if the seconds between the temporals cannot be obtained
 484      * @throws ArithmeticException if the calculation exceeds the capacity of {@code Duration}
 485      */
 486     public static Duration between(Temporal startInclusive, Temporal endExclusive) {
 487         try {
 488             return ofNanos(startInclusive.until(endExclusive, NANOS));
 489         } catch (DateTimeException | ArithmeticException ex) {
 490             long secs = startInclusive.until(endExclusive, SECONDS);
 491             long nanos;
 492             try {
 493                 nanos = endExclusive.getLong(NANO_OF_SECOND) - startInclusive.getLong(NANO_OF_SECOND);
 494                 if (secs > 0 && nanos < 0) {
 495                     secs++;
 496                 } else if (secs < 0 && nanos > 0) {
 497                     secs--;
 498                 }
 499             } catch (DateTimeException ex2) {
 500                 nanos = 0;
 501             }
 502             return ofSeconds(secs, nanos);
 503         }
 504     }
 505 
 506     //-----------------------------------------------------------------------
 507     /**
 508      * Obtains an instance of {@code Duration} using seconds and nanoseconds.
 509      *
 510      * @param seconds  the length of the duration in seconds, positive or negative
 511      * @param nanoAdjustment  the nanosecond adjustment within the second, from 0 to 999,999,999
 512      */
 513     private static Duration create(long seconds, int nanoAdjustment) {
 514         if ((seconds | nanoAdjustment) == 0) {
 515             return ZERO;
 516         }
 517         return new Duration(seconds, nanoAdjustment);
 518     }
 519 
 520     /**
 521      * Constructs an instance of {@code Duration} using seconds and nanoseconds.
 522      *
 523      * @param seconds  the length of the duration in seconds, positive or negative
 524      * @param nanos  the nanoseconds within the second, from 0 to 999,999,999
 525      */
 526     private Duration(long seconds, int nanos) {
 527         super();
 528         this.seconds = seconds;
 529         this.nanos = nanos;
 530     }
 531 
 532     //-----------------------------------------------------------------------
 533     /**
 534      * Gets the value of the requested unit.
 535      * <p>
 536      * This returns a value for each of the two supported units,
 537      * {@link ChronoUnit#SECONDS SECONDS} and {@link ChronoUnit#NANOS NANOS}.
 538      * All other units throw an exception.
 539      *
 540      * @param unit the {@code TemporalUnit} for which to return the value
 541      * @return the long value of the unit
 542      * @throws DateTimeException if the unit is not supported
 543      * @throws UnsupportedTemporalTypeException if the unit is not supported
 544      */
 545     @Override
 546     public long get(TemporalUnit unit) {
 547         if (unit == SECONDS) {
 548             return seconds;
 549         } else if (unit == NANOS) {
 550             return nanos;
 551         } else {
 552             throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
 553         }
 554     }
 555 
 556     /**
 557      * Gets the set of units supported by this duration.
 558      * <p>
 559      * The supported units are {@link ChronoUnit#SECONDS SECONDS},
 560      * and {@link ChronoUnit#NANOS NANOS}.
 561      * They are returned in the order seconds, nanos.
 562      * <p>
 563      * This set can be used in conjunction with {@link #get(TemporalUnit)}
 564      * to access the entire state of the duration.
 565      *
 566      * @return a list containing the seconds and nanos units, not null
 567      */
 568     @Override
 569     public List<TemporalUnit> getUnits() {
 570         return DurationUnits.UNITS;
 571     }
 572 
 573     /**
 574      * Private class to delay initialization of this list until needed.
 575      * The circular dependency between Duration and ChronoUnit prevents
 576      * the simple initialization in Duration.
 577      */
 578     private static class DurationUnits {
 579         static final List<TemporalUnit> UNITS =
 580                 Collections.unmodifiableList(Arrays.<TemporalUnit>asList(SECONDS, NANOS));
 581     }
 582 
 583     //-----------------------------------------------------------------------
 584     /**
 585      * Checks if this duration is zero length.
 586      * <p>
 587      * A {@code Duration} represents a directed distance between two points on
 588      * the time-line and can therefore be positive, zero or negative.
 589      * This method checks whether the length is zero.
 590      *
 591      * @return true if this duration has a total length equal to zero
 592      */
 593     public boolean isZero() {
 594         return (seconds | nanos) == 0;
 595     }
 596 
 597     /**
 598      * Checks if this duration is negative, excluding zero.
 599      * <p>
 600      * A {@code Duration} represents a directed distance between two points on
 601      * the time-line and can therefore be positive, zero or negative.
 602      * This method checks whether the length is less than zero.
 603      *
 604      * @return true if this duration has a total length less than zero
 605      */
 606     public boolean isNegative() {
 607         return seconds < 0;
 608     }
 609 
 610     //-----------------------------------------------------------------------
 611     /**
 612      * Gets the number of seconds in this duration.
 613      * <p>
 614      * The length of the duration is stored using two fields - seconds and nanoseconds.
 615      * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 616      * the length in seconds.
 617      * The total duration is defined by calling this method and {@link #getNano()}.
 618      * <p>
 619      * A {@code Duration} represents a directed distance between two points on the time-line.
 620      * A negative duration is expressed by the negative sign of the seconds part.
 621      * A duration of -1 nanosecond is stored as -1 seconds plus 999,999,999 nanoseconds.
 622      *
 623      * @return the whole seconds part of the length of the duration, positive or negative
 624      */
 625     public long getSeconds() {
 626         return seconds;
 627     }
 628 
 629     /**
 630      * Gets the number of nanoseconds within the second in this duration.
 631      * <p>
 632      * The length of the duration is stored using two fields - seconds and nanoseconds.
 633      * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 634      * the length in seconds.
 635      * The total duration is defined by calling this method and {@link #getSeconds()}.
 636      * <p>
 637      * A {@code Duration} represents a directed distance between two points on the time-line.
 638      * A negative duration is expressed by the negative sign of the seconds part.
 639      * A duration of -1 nanosecond is stored as -1 seconds plus 999,999,999 nanoseconds.
 640      *
 641      * @return the nanoseconds within the second part of the length of the duration, from 0 to 999,999,999
 642      */
 643     public int getNano() {
 644         return nanos;
 645     }
 646 
 647     //-----------------------------------------------------------------------
 648     /**
 649      * Returns a copy of this duration with the specified amount of seconds.
 650      * <p>
 651      * This returns a duration with the specified seconds, retaining the
 652      * nano-of-second part of this duration.
 653      * <p>
 654      * This instance is immutable and unaffected by this method call.
 655      *
 656      * @param seconds  the seconds to represent, may be negative
 657      * @return a {@code Duration} based on this period with the requested seconds, not null
 658      */
 659     public Duration withSeconds(long seconds) {
 660         return create(seconds, nanos);
 661     }
 662 
 663     /**
 664      * Returns a copy of this duration with the specified nano-of-second.
 665      * <p>
 666      * This returns a duration with the specified nano-of-second, retaining the
 667      * seconds part of this duration.
 668      * <p>
 669      * This instance is immutable and unaffected by this method call.
 670      *
 671      * @param nanoOfSecond  the nano-of-second to represent, from 0 to 999,999,999
 672      * @return a {@code Duration} based on this period with the requested nano-of-second, not null
 673      * @throws DateTimeException if the nano-of-second is invalid
 674      */
 675     public Duration withNanos(int nanoOfSecond) {
 676         NANO_OF_SECOND.checkValidIntValue(nanoOfSecond);
 677         return create(seconds, nanoOfSecond);
 678     }
 679 
 680     //-----------------------------------------------------------------------
 681     /**
 682      * Returns a copy of this duration with the specified duration added.
 683      * <p>
 684      * This instance is immutable and unaffected by this method call.
 685      *
 686      * @param duration  the duration to add, positive or negative, not null
 687      * @return a {@code Duration} based on this duration with the specified duration added, not null
 688      * @throws ArithmeticException if numeric overflow occurs
 689      */
 690     public Duration plus(Duration duration) {
 691         return plus(duration.getSeconds(), duration.getNano());
 692      }
 693 
 694     /**
 695      * Returns a copy of this duration with the specified duration added.
 696      * <p>
 697      * The duration amount is measured in terms of the specified unit.
 698      * Only a subset of units are accepted by this method.
 699      * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 700      * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 701      * <p>
 702      * This instance is immutable and unaffected by this method call.
 703      *
 704      * @param amountToAdd  the amount to add, measured in terms of the unit, positive or negative
 705      * @param unit  the unit that the amount is measured in, must have an exact duration, not null
 706      * @return a {@code Duration} based on this duration with the specified duration added, not null
 707      * @throws UnsupportedTemporalTypeException if the unit is not supported
 708      * @throws ArithmeticException if numeric overflow occurs
 709      */
 710     public Duration plus(long amountToAdd, TemporalUnit unit) {
 711         Objects.requireNonNull(unit, "unit");
 712         if (unit == DAYS) {
 713             return plus(Math.multiplyExact(amountToAdd, SECONDS_PER_DAY), 0);
 714         }
 715         if (unit.isDurationEstimated()) {
 716             throw new UnsupportedTemporalTypeException("Unit must not have an estimated duration");
 717         }
 718         if (amountToAdd == 0) {
 719             return this;
 720         }
 721         if (unit instanceof ChronoUnit) {
 722             switch ((ChronoUnit) unit) {
 723                 case NANOS: return plusNanos(amountToAdd);
 724                 case MICROS: return plusSeconds((amountToAdd / (1000_000L * 1000)) * 1000).plusNanos((amountToAdd % (1000_000L * 1000)) * 1000);
 725                 case MILLIS: return plusMillis(amountToAdd);
 726                 case SECONDS: return plusSeconds(amountToAdd);
 727             }
 728             return plusSeconds(Math.multiplyExact(unit.getDuration().seconds, amountToAdd));
 729         }
 730         Duration duration = unit.getDuration().multipliedBy(amountToAdd);
 731         return plusSeconds(duration.getSeconds()).plusNanos(duration.getNano());
 732     }
 733 
 734     //-----------------------------------------------------------------------
 735     /**
 736      * Returns a copy of this duration with the specified duration in standard 24 hour days added.
 737      * <p>
 738      * The number of days is multiplied by 86400 to obtain the number of seconds to add.
 739      * This is based on the standard definition of a day as 24 hours.
 740      * <p>
 741      * This instance is immutable and unaffected by this method call.
 742      *
 743      * @param daysToAdd  the days to add, positive or negative
 744      * @return a {@code Duration} based on this duration with the specified days added, not null
 745      * @throws ArithmeticException if numeric overflow occurs
 746      */
 747     public Duration plusDays(long daysToAdd) {
 748         return plus(Math.multiplyExact(daysToAdd, SECONDS_PER_DAY), 0);
 749     }
 750 
 751     /**
 752      * Returns a copy of this duration with the specified duration in hours added.
 753      * <p>
 754      * This instance is immutable and unaffected by this method call.
 755      *
 756      * @param hoursToAdd  the hours to add, positive or negative
 757      * @return a {@code Duration} based on this duration with the specified hours added, not null
 758      * @throws ArithmeticException if numeric overflow occurs
 759      */
 760     public Duration plusHours(long hoursToAdd) {
 761         return plus(Math.multiplyExact(hoursToAdd, SECONDS_PER_HOUR), 0);
 762     }
 763 
 764     /**
 765      * Returns a copy of this duration with the specified duration in minutes added.
 766      * <p>
 767      * This instance is immutable and unaffected by this method call.
 768      *
 769      * @param minutesToAdd  the minutes to add, positive or negative
 770      * @return a {@code Duration} based on this duration with the specified minutes added, not null
 771      * @throws ArithmeticException if numeric overflow occurs
 772      */
 773     public Duration plusMinutes(long minutesToAdd) {
 774         return plus(Math.multiplyExact(minutesToAdd, SECONDS_PER_MINUTE), 0);
 775     }
 776 
 777     /**
 778      * Returns a copy of this duration with the specified duration in seconds added.
 779      * <p>
 780      * This instance is immutable and unaffected by this method call.
 781      *
 782      * @param secondsToAdd  the seconds to add, positive or negative
 783      * @return a {@code Duration} based on this duration with the specified seconds added, not null
 784      * @throws ArithmeticException if numeric overflow occurs
 785      */
 786     public Duration plusSeconds(long secondsToAdd) {
 787         return plus(secondsToAdd, 0);
 788     }
 789 
 790     /**
 791      * Returns a copy of this duration with the specified duration in milliseconds added.
 792      * <p>
 793      * This instance is immutable and unaffected by this method call.
 794      *
 795      * @param millisToAdd  the milliseconds to add, positive or negative
 796      * @return a {@code Duration} based on this duration with the specified milliseconds added, not null
 797      * @throws ArithmeticException if numeric overflow occurs
 798      */
 799     public Duration plusMillis(long millisToAdd) {
 800         return plus(millisToAdd / 1000, (millisToAdd % 1000) * 1000_000);
 801     }
 802 
 803     /**
 804      * Returns a copy of this duration with the specified duration in nanoseconds added.
 805      * <p>
 806      * This instance is immutable and unaffected by this method call.
 807      *
 808      * @param nanosToAdd  the nanoseconds to add, positive or negative
 809      * @return a {@code Duration} based on this duration with the specified nanoseconds added, not null
 810      * @throws ArithmeticException if numeric overflow occurs
 811      */
 812     public Duration plusNanos(long nanosToAdd) {
 813         return plus(0, nanosToAdd);
 814     }
 815 
 816     /**
 817      * Returns a copy of this duration with the specified duration added.
 818      * <p>
 819      * This instance is immutable and unaffected by this method call.
 820      *
 821      * @param secondsToAdd  the seconds to add, positive or negative
 822      * @param nanosToAdd  the nanos to add, positive or negative
 823      * @return a {@code Duration} based on this duration with the specified seconds added, not null
 824      * @throws ArithmeticException if numeric overflow occurs
 825      */
 826     private Duration plus(long secondsToAdd, long nanosToAdd) {
 827         if ((secondsToAdd | nanosToAdd) == 0) {
 828             return this;
 829         }
 830         long epochSec = Math.addExact(seconds, secondsToAdd);
 831         epochSec = Math.addExact(epochSec, nanosToAdd / NANOS_PER_SECOND);
 832         nanosToAdd = nanosToAdd % NANOS_PER_SECOND;
 833         long nanoAdjustment = nanos + nanosToAdd;  // safe int+NANOS_PER_SECOND
 834         return ofSeconds(epochSec, nanoAdjustment);
 835     }
 836 
 837     //-----------------------------------------------------------------------
 838     /**
 839      * Returns a copy of this duration with the specified duration subtracted.
 840      * <p>
 841      * This instance is immutable and unaffected by this method call.
 842      *
 843      * @param duration  the duration to subtract, positive or negative, not null
 844      * @return a {@code Duration} based on this duration with the specified duration subtracted, not null
 845      * @throws ArithmeticException if numeric overflow occurs
 846      */
 847     public Duration minus(Duration duration) {
 848         long secsToSubtract = duration.getSeconds();
 849         int nanosToSubtract = duration.getNano();
 850         if (secsToSubtract == Long.MIN_VALUE) {
 851             return plus(Long.MAX_VALUE, -nanosToSubtract).plus(1, 0);
 852         }
 853         return plus(-secsToSubtract, -nanosToSubtract);
 854      }
 855 
 856     /**
 857      * Returns a copy of this duration with the specified duration subtracted.
 858      * <p>
 859      * The duration amount is measured in terms of the specified unit.
 860      * Only a subset of units are accepted by this method.
 861      * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 862      * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 863      * <p>
 864      * This instance is immutable and unaffected by this method call.
 865      *
 866      * @param amountToSubtract  the amount to subtract, measured in terms of the unit, positive or negative
 867      * @param unit  the unit that the amount is measured in, must have an exact duration, not null
 868      * @return a {@code Duration} based on this duration with the specified duration subtracted, not null
 869      * @throws ArithmeticException if numeric overflow occurs
 870      */
 871     public Duration minus(long amountToSubtract, TemporalUnit unit) {
 872         return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
 873     }
 874 
 875     //-----------------------------------------------------------------------
 876     /**
 877      * Returns a copy of this duration with the specified duration in standard 24 hour days subtracted.
 878      * <p>
 879      * The number of days is multiplied by 86400 to obtain the number of seconds to subtract.
 880      * This is based on the standard definition of a day as 24 hours.
 881      * <p>
 882      * This instance is immutable and unaffected by this method call.
 883      *
 884      * @param daysToSubtract  the days to subtract, positive or negative
 885      * @return a {@code Duration} based on this duration with the specified days subtracted, not null
 886      * @throws ArithmeticException if numeric overflow occurs
 887      */
 888     public Duration minusDays(long daysToSubtract) {
 889         return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
 890     }
 891 
 892     /**
 893      * Returns a copy of this duration with the specified duration in hours subtracted.
 894      * <p>
 895      * The number of hours is multiplied by 3600 to obtain the number of seconds to subtract.
 896      * <p>
 897      * This instance is immutable and unaffected by this method call.
 898      *
 899      * @param hoursToSubtract  the hours to subtract, positive or negative
 900      * @return a {@code Duration} based on this duration with the specified hours subtracted, not null
 901      * @throws ArithmeticException if numeric overflow occurs
 902      */
 903     public Duration minusHours(long hoursToSubtract) {
 904         return (hoursToSubtract == Long.MIN_VALUE ? plusHours(Long.MAX_VALUE).plusHours(1) : plusHours(-hoursToSubtract));
 905     }
 906 
 907     /**
 908      * Returns a copy of this duration with the specified duration in minutes subtracted.
 909      * <p>
 910      * The number of hours is multiplied by 60 to obtain the number of seconds to subtract.
 911      * <p>
 912      * This instance is immutable and unaffected by this method call.
 913      *
 914      * @param minutesToSubtract  the minutes to subtract, positive or negative
 915      * @return a {@code Duration} based on this duration with the specified minutes subtracted, not null
 916      * @throws ArithmeticException if numeric overflow occurs
 917      */
 918     public Duration minusMinutes(long minutesToSubtract) {
 919         return (minutesToSubtract == Long.MIN_VALUE ? plusMinutes(Long.MAX_VALUE).plusMinutes(1) : plusMinutes(-minutesToSubtract));
 920     }
 921 
 922     /**
 923      * Returns a copy of this duration with the specified duration in seconds subtracted.
 924      * <p>
 925      * This instance is immutable and unaffected by this method call.
 926      *
 927      * @param secondsToSubtract  the seconds to subtract, positive or negative
 928      * @return a {@code Duration} based on this duration with the specified seconds subtracted, not null
 929      * @throws ArithmeticException if numeric overflow occurs
 930      */
 931     public Duration minusSeconds(long secondsToSubtract) {
 932         return (secondsToSubtract == Long.MIN_VALUE ? plusSeconds(Long.MAX_VALUE).plusSeconds(1) : plusSeconds(-secondsToSubtract));
 933     }
 934 
 935     /**
 936      * Returns a copy of this duration with the specified duration in milliseconds subtracted.
 937      * <p>
 938      * This instance is immutable and unaffected by this method call.
 939      *
 940      * @param millisToSubtract  the milliseconds to subtract, positive or negative
 941      * @return a {@code Duration} based on this duration with the specified milliseconds subtracted, not null
 942      * @throws ArithmeticException if numeric overflow occurs
 943      */
 944     public Duration minusMillis(long millisToSubtract) {
 945         return (millisToSubtract == Long.MIN_VALUE ? plusMillis(Long.MAX_VALUE).plusMillis(1) : plusMillis(-millisToSubtract));
 946     }
 947 
 948     /**
 949      * Returns a copy of this duration with the specified duration in nanoseconds subtracted.
 950      * <p>
 951      * This instance is immutable and unaffected by this method call.
 952      *
 953      * @param nanosToSubtract  the nanoseconds to subtract, positive or negative
 954      * @return a {@code Duration} based on this duration with the specified nanoseconds subtracted, not null
 955      * @throws ArithmeticException if numeric overflow occurs
 956      */
 957     public Duration minusNanos(long nanosToSubtract) {
 958         return (nanosToSubtract == Long.MIN_VALUE ? plusNanos(Long.MAX_VALUE).plusNanos(1) : plusNanos(-nanosToSubtract));
 959     }
 960 
 961     //-----------------------------------------------------------------------
 962     /**
 963      * Returns a copy of this duration multiplied by the scalar.
 964      * <p>
 965      * This instance is immutable and unaffected by this method call.
 966      *
 967      * @param multiplicand  the value to multiply the duration by, positive or negative
 968      * @return a {@code Duration} based on this duration multiplied by the specified scalar, not null
 969      * @throws ArithmeticException if numeric overflow occurs
 970      */
 971     public Duration multipliedBy(long multiplicand) {
 972         if (multiplicand == 0) {
 973             return ZERO;
 974         }
 975         if (multiplicand == 1) {
 976             return this;
 977         }
 978         return create(toBigDecimalSeconds().multiply(BigDecimal.valueOf(multiplicand)));
 979      }
 980 
 981     /**
 982      * Returns a copy of this duration divided by the specified value.
 983      * <p>
 984      * This instance is immutable and unaffected by this method call.
 985      *
 986      * @param divisor  the value to divide the duration by, positive or negative, not zero
 987      * @return a {@code Duration} based on this duration divided by the specified divisor, not null
 988      * @throws ArithmeticException if the divisor is zero or if numeric overflow occurs
 989      */
 990     public Duration dividedBy(long divisor) {
 991         if (divisor == 0) {
 992             throw new ArithmeticException("Cannot divide by zero");
 993         }
 994         if (divisor == 1) {
 995             return this;
 996         }
 997         return create(toBigDecimalSeconds().divide(BigDecimal.valueOf(divisor), RoundingMode.DOWN));
 998      }
 999 
1000     /**
1001      * Returns number of whole times a specified Duration occurs within this Duration.
1002      * <p>
1003      * This instance is immutable and unaffected by this method call.
1004      *
1005      * @param divisor the value to divide the duration by, positive or negative, not null
1006      * @return number of whole times, rounded toward zero, a specified
1007      *         {@code Duration} occurs within this Duration, may be negative
1008      * @throws ArithmeticException if the divisor is zero, or if numeric overflow occurs
1009      * @since 9
1010      */
1011     public long dividedBy(Duration divisor) {
1012         Objects.requireNonNull(divisor, "divisor");
1013         BigDecimal dividendBigD = toBigDecimalSeconds();
1014         BigDecimal divisorBigD = divisor.toBigDecimalSeconds();
1015         return dividendBigD.divideToIntegralValue(divisorBigD).longValueExact();
1016     }
1017 
1018     /**
1019      * Converts this duration to the total length in seconds and
1020      * fractional nanoseconds expressed as a {@code BigDecimal}.
1021      *
1022      * @return the total length of the duration in seconds, with a scale of 9, not null
1023      */
1024     private BigDecimal toBigDecimalSeconds() {
1025         return BigDecimal.valueOf(seconds).add(BigDecimal.valueOf(nanos, 9));
1026     }
1027 
1028     /**
1029      * Creates an instance of {@code Duration} from a number of seconds.
1030      *
1031      * @param seconds  the number of seconds, up to scale 9, positive or negative
1032      * @return a {@code Duration}, not null
1033      * @throws ArithmeticException if numeric overflow occurs
1034      */
1035     private static Duration create(BigDecimal seconds) {
1036         BigInteger nanos = seconds.movePointRight(9).toBigIntegerExact();
1037         BigInteger[] divRem = nanos.divideAndRemainder(BI_NANOS_PER_SECOND);
1038         if (divRem[0].bitLength() > 63) {
1039             throw new ArithmeticException("Exceeds capacity of Duration: " + nanos);
1040         }
1041         return ofSeconds(divRem[0].longValue(), divRem[1].intValue());
1042     }
1043 
1044     //-----------------------------------------------------------------------
1045     /**
1046      * Returns a copy of this duration with the length negated.
1047      * <p>
1048      * This method swaps the sign of the total length of this duration.
1049      * For example, {@code PT1.3S} will be returned as {@code PT-1.3S}.
1050      * <p>
1051      * This instance is immutable and unaffected by this method call.
1052      *
1053      * @return a {@code Duration} based on this duration with the amount negated, not null
1054      * @throws ArithmeticException if numeric overflow occurs
1055      */
1056     public Duration negated() {
1057         return multipliedBy(-1);
1058     }
1059 
1060     /**
1061      * Returns a copy of this duration with a positive length.
1062      * <p>
1063      * This method returns a positive duration by effectively removing the sign from any negative total length.
1064      * For example, {@code PT-1.3S} will be returned as {@code PT1.3S}.
1065      * <p>
1066      * This instance is immutable and unaffected by this method call.
1067      *
1068      * @return a {@code Duration} based on this duration with an absolute length, not null
1069      * @throws ArithmeticException if numeric overflow occurs
1070      */
1071     public Duration abs() {
1072         return isNegative() ? negated() : this;
1073     }
1074 
1075     //-------------------------------------------------------------------------
1076     /**
1077      * Adds this duration to the specified temporal object.
1078      * <p>
1079      * This returns a temporal object of the same observable type as the input
1080      * with this duration added.
1081      * <p>
1082      * In most cases, it is clearer to reverse the calling pattern by using
1083      * {@link Temporal#plus(TemporalAmount)}.
1084      * <pre>
1085      *   // these two lines are equivalent, but the second approach is recommended
1086      *   dateTime = thisDuration.addTo(dateTime);
1087      *   dateTime = dateTime.plus(thisDuration);
1088      * </pre>
1089      * <p>
1090      * The calculation will add the seconds, then nanos.
1091      * Only non-zero amounts will be added.
1092      * <p>
1093      * This instance is immutable and unaffected by this method call.
1094      *
1095      * @param temporal  the temporal object to adjust, not null
1096      * @return an object of the same type with the adjustment made, not null
1097      * @throws DateTimeException if unable to add
1098      * @throws ArithmeticException if numeric overflow occurs
1099      */
1100     @Override
1101     public Temporal addTo(Temporal temporal) {
1102         if (seconds != 0) {
1103             temporal = temporal.plus(seconds, SECONDS);
1104         }
1105         if (nanos != 0) {
1106             temporal = temporal.plus(nanos, NANOS);
1107         }
1108         return temporal;
1109     }
1110 
1111     /**
1112      * Subtracts this duration from the specified temporal object.
1113      * <p>
1114      * This returns a temporal object of the same observable type as the input
1115      * with this duration subtracted.
1116      * <p>
1117      * In most cases, it is clearer to reverse the calling pattern by using
1118      * {@link Temporal#minus(TemporalAmount)}.
1119      * <pre>
1120      *   // these two lines are equivalent, but the second approach is recommended
1121      *   dateTime = thisDuration.subtractFrom(dateTime);
1122      *   dateTime = dateTime.minus(thisDuration);
1123      * </pre>
1124      * <p>
1125      * The calculation will subtract the seconds, then nanos.
1126      * Only non-zero amounts will be added.
1127      * <p>
1128      * This instance is immutable and unaffected by this method call.
1129      *
1130      * @param temporal  the temporal object to adjust, not null
1131      * @return an object of the same type with the adjustment made, not null
1132      * @throws DateTimeException if unable to subtract
1133      * @throws ArithmeticException if numeric overflow occurs
1134      */
1135     @Override
1136     public Temporal subtractFrom(Temporal temporal) {
1137         if (seconds != 0) {
1138             temporal = temporal.minus(seconds, SECONDS);
1139         }
1140         if (nanos != 0) {
1141             temporal = temporal.minus(nanos, NANOS);
1142         }
1143         return temporal;
1144     }
1145 
1146     //-----------------------------------------------------------------------
1147     /**
1148      * Gets the number of days in this duration.
1149      * <p>
1150      * This returns the total number of days in the duration by dividing the
1151      * number of seconds by 86400.
1152      * This is based on the standard definition of a day as 24 hours.
1153      * <p>
1154      * This instance is immutable and unaffected by this method call.
1155      *
1156      * @return the number of days in the duration, may be negative
1157      */
1158     public long toDays() {
1159         return seconds / SECONDS_PER_DAY;
1160     }
1161 
1162     /**
1163      * Gets the number of hours in this duration.
1164      * <p>
1165      * This returns the total number of hours in the duration by dividing the
1166      * number of seconds by 3600.
1167      * <p>
1168      * This instance is immutable and unaffected by this method call.
1169      *
1170      * @return the number of hours in the duration, may be negative
1171      */
1172     public long toHours() {
1173         return seconds / SECONDS_PER_HOUR;
1174     }
1175 
1176     /**
1177      * Gets the number of minutes in this duration.
1178      * <p>
1179      * This returns the total number of minutes in the duration by dividing the
1180      * number of seconds by 60.
1181      * <p>
1182      * This instance is immutable and unaffected by this method call.
1183      *
1184      * @return the number of minutes in the duration, may be negative
1185      */
1186     public long toMinutes() {
1187         return seconds / SECONDS_PER_MINUTE;
1188     }
1189 
1190     /**
1191      * Gets the number of seconds in this duration.
1192      * <p>
1193      * This returns the total number of whole seconds in the duration.
1194      * <p>
1195      * This instance is immutable and unaffected by this method call.
1196      *
1197      * @return the whole seconds part of the length of the duration, positive or negative
1198      * @since 9
1199      */
1200     public long toSeconds() {
1201         return seconds;
1202     }
1203 
1204     /**
1205      * Converts this duration to the total length in milliseconds.
1206      * <p>
1207      * If this duration is too large to fit in a {@code long} milliseconds, then an
1208      * exception is thrown.
1209      * <p>
1210      * If this duration has greater than millisecond precision, then the conversion
1211      * will drop any excess precision information as though the amount in nanoseconds
1212      * was subject to integer division by one million.
1213      *
1214      * @return the total length of the duration in milliseconds
1215      * @throws ArithmeticException if numeric overflow occurs
1216      */
1217     public long toMillis() {
1218         long tempSeconds = seconds;
1219         long tempNanos = nanos;
1220         if (tempSeconds < 0) {
1221             // change the seconds and nano value to
1222             // handle Long.MIN_VALUE case
1223             tempSeconds = tempSeconds + 1;
1224             tempNanos = tempNanos - NANOS_PER_SECOND;
1225         }
1226         long millis = Math.multiplyExact(tempSeconds, 1000);
1227         millis = Math.addExact(millis, tempNanos / NANOS_PER_MILLI);
1228         return millis;
1229     }
1230 
1231     /**
1232      * Converts this duration to the total length in nanoseconds expressed as a {@code long}.
1233      * <p>
1234      * If this duration is too large to fit in a {@code long} nanoseconds, then an
1235      * exception is thrown.
1236      *
1237      * @return the total length of the duration in nanoseconds
1238      * @throws ArithmeticException if numeric overflow occurs
1239      */
1240     public long toNanos() {
1241         long tempSeconds = seconds;
1242         long tempNanos = nanos;
1243         if (tempSeconds < 0) {
1244             // change the seconds and nano value to
1245             // handle Long.MIN_VALUE case
1246             tempSeconds = tempSeconds + 1;
1247             tempNanos = tempNanos - NANOS_PER_SECOND;
1248         }
1249         long totalNanos = Math.multiplyExact(tempSeconds, NANOS_PER_SECOND);
1250         totalNanos = Math.addExact(totalNanos, tempNanos);
1251         return totalNanos;
1252     }
1253 
1254     /**
1255      * Extracts the number of days in the duration.
1256      * <p>
1257      * This returns the total number of days in the duration by dividing the
1258      * number of seconds by 86400.
1259      * This is based on the standard definition of a day as 24 hours.
1260      * <p>
1261      * This instance is immutable and unaffected by this method call.
1262      *
1263      * @return the number of days in the duration, may be negative
1264      * @since 9
1265      */
1266     public long toDaysPart(){
1267         return seconds / SECONDS_PER_DAY;
1268     }
1269 
1270     /**
1271      * Extracts the number of hours part in the duration.
1272      * <p>
1273      * This returns the number of remaining hours when dividing {@link #toHours}
1274      * by hours in a day.
1275      * This is based on the standard definition of a day as 24 hours.
1276      * <p>
1277      * This instance is immutable and unaffected by this method call.
1278      *
1279      * @return the number of hours part in the duration, may be negative
1280      * @since 9
1281      */
1282     public int toHoursPart(){
1283         return (int) (toHours() % 24);
1284     }
1285 
1286     /**
1287      * Extracts the number of minutes part in the duration.
1288      * <p>
1289      * This returns the number of remaining minutes when dividing {@link #toMinutes}
1290      * by minutes in an hour.
1291      * This is based on the standard definition of an hour as 60 minutes.
1292      * <p>
1293      * This instance is immutable and unaffected by this method call.
1294      *
1295      * @return the number of minutes parts in the duration, may be negative
1296      * @since 9
1297      */
1298     public int toMinutesPart(){
1299         return (int) (toMinutes() % MINUTES_PER_HOUR);
1300     }
1301 
1302     /**
1303      * Extracts the number of seconds part in the duration.
1304      * <p>
1305      * This returns the remaining seconds when dividing {@link #toSeconds}
1306      * by seconds in a minute.
1307      * This is based on the standard definition of a minute as 60 seconds.
1308      * <p>
1309      * This instance is immutable and unaffected by this method call.
1310      *
1311      * @return the number of seconds parts in the duration, may be negative
1312      * @since 9
1313      */
1314     public int toSecondsPart(){
1315         return (int) (seconds % SECONDS_PER_MINUTE);
1316     }
1317 
1318     /**
1319      * Extracts the number of milliseconds part of the duration.
1320      * <p>
1321      * This returns the milliseconds part by dividing the number of nanoseconds by 1,000,000.
1322      * The length of the duration is stored using two fields - seconds and nanoseconds.
1323      * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
1324      * the length in seconds.
1325      * The total duration is defined by calling {@link #getNano()} and {@link #getSeconds()}.
1326      * <p>
1327      * This instance is immutable and unaffected by this method call.
1328      *
1329      * @return the number of milliseconds part of the duration.
1330      * @since 9
1331      */
1332     public int toMillisPart(){
1333         return nanos / 1000_000;
1334     }
1335 
1336     /**
1337      * Get the nanoseconds part within seconds of the duration.
1338      * <p>
1339      * The length of the duration is stored using two fields - seconds and nanoseconds.
1340      * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
1341      * the length in seconds.
1342      * The total duration is defined by calling {@link #getNano()} and {@link #getSeconds()}.
1343      * <p>
1344      * This instance is immutable and unaffected by this method call.
1345      *
1346      * @return the nanoseconds within the second part of the length of the duration, from 0 to 999,999,999
1347      * @since 9
1348      */
1349     public int toNanosPart(){
1350         return nanos;
1351     }
1352 
1353 
1354     //-----------------------------------------------------------------------
1355     /**
1356      * Returns a copy of this {@code Duration} truncated to the specified unit.
1357      * <p>
1358      * Truncating the duration returns a copy of the original with fields
1359      * smaller than the specified unit set to zero.
1360      * For example, truncating with the {@link ChronoUnit#MINUTES MINUTES} unit will
1361      * round down to the nearest minute, setting the seconds and nanoseconds to zero.
1362      * <p>
1363      * The unit must have a {@linkplain TemporalUnit#getDuration() duration}
1364      * that divides into the length of a standard day without remainder.
1365      * This includes all supplied time units on {@link ChronoUnit} and
1366      * {@link ChronoUnit#DAYS DAYS}. Other ChronoUnits throw an exception.
1367      * <p>
1368      * This instance is immutable and unaffected by this method call.
1369      *
1370      * @param unit the unit to truncate to, not null
1371      * @return a {@code Duration} based on this duration with the time truncated, not null
1372      * @throws DateTimeException if the unit is invalid for truncation
1373      * @throws UnsupportedTemporalTypeException if the unit is not supported
1374      */
1375     public Duration truncatedTo(TemporalUnit unit) {
1376         Objects.requireNonNull(unit, "unit");
1377         if (unit == ChronoUnit.SECONDS) {
1378             return new Duration(seconds, 0);
1379         } else if (unit == ChronoUnit.NANOS) {
1380             return this;
1381         }
1382         Duration unitDur = unit.getDuration();
1383         if (unitDur.getSeconds() > LocalTime.SECONDS_PER_DAY) {
1384             throw new UnsupportedTemporalTypeException("Unit is too large to be used for truncation");
1385         }
1386         long dur = unitDur.toNanos();
1387         if ((LocalTime.NANOS_PER_DAY % dur) != 0) {
1388             throw new UnsupportedTemporalTypeException("Unit must divide into a standard day without remainder");
1389         }
1390         long nod = (seconds % LocalTime.SECONDS_PER_DAY) * LocalTime.NANOS_PER_SECOND + nanos;
1391         long result = Math.floorDiv(nod, dur) * dur ;
1392         return plusNanos(result - nod);
1393     }
1394 
1395     //-----------------------------------------------------------------------
1396     /**
1397      * Compares this duration to the specified {@code Duration}.
1398      * <p>
1399      * The comparison is based on the total length of the durations.
1400      * It is "consistent with equals", as defined by {@link Comparable}.
1401      *
1402      * @param otherDuration the other duration to compare to, not null
1403      * @return the comparator value, negative if less, positive if greater
1404      */
1405     @Override
1406     public int compareTo(Duration otherDuration) {
1407         int cmp = Long.compare(seconds, otherDuration.seconds);
1408         if (cmp != 0) {
1409             return cmp;
1410         }
1411         return nanos - otherDuration.nanos;
1412     }
1413 
1414     //-----------------------------------------------------------------------
1415     /**
1416      * Checks if this duration is equal to the specified {@code Duration}.
1417      * <p>
1418      * The comparison is based on the total length of the durations.
1419      *
1420      * @param otherDuration the other duration, null returns false
1421      * @return true if the other duration is equal to this one
1422      */
1423     @Override
1424     public boolean equals(Object otherDuration) {
1425         if (this == otherDuration) {
1426             return true;
1427         }
1428         if (otherDuration instanceof Duration) {
1429             Duration other = (Duration) otherDuration;
1430             return this.seconds == other.seconds &&
1431                    this.nanos == other.nanos;
1432         }
1433         return false;
1434     }
1435 
1436     /**
1437      * A hash code for this duration.
1438      *
1439      * @return a suitable hash code
1440      */
1441     @Override
1442     public int hashCode() {
1443         return ((int) (seconds ^ (seconds >>> 32))) + (51 * nanos);
1444     }
1445 
1446     //-----------------------------------------------------------------------
1447     /**
1448      * A string representation of this duration using ISO-8601 seconds
1449      * based representation, such as {@code PT8H6M12.345S}.
1450      * <p>
1451      * The format of the returned string will be {@code PTnHnMnS}, where n is
1452      * the relevant hours, minutes or seconds part of the duration.
1453      * Any fractional seconds are placed after a decimal point in the seconds section.
1454      * If a section has a zero value, it is omitted.
1455      * The hours, minutes and seconds will all have the same sign.
1456      * <p>
1457      * Examples:
1458      * <pre>
1459      *    "20.345 seconds"                 -- "PT20.345S
1460      *    "15 minutes" (15 * 60 seconds)   -- "PT15M"
1461      *    "10 hours" (10 * 3600 seconds)   -- "PT10H"
1462      *    "2 days" (2 * 86400 seconds)     -- "PT48H"
1463      * </pre>
1464      * Note that multiples of 24 hours are not output as days to avoid confusion
1465      * with {@code Period}.
1466      *
1467      * @return an ISO-8601 representation of this duration, not null
1468      */
1469     @Override
1470     public String toString() {
1471         if (this == ZERO) {
1472             return "PT0S";
1473         }
1474         long effectiveTotalSecs = seconds;
1475         if (seconds < 0 && nanos > 0) {
1476             effectiveTotalSecs++;
1477         }
1478         long hours = effectiveTotalSecs / SECONDS_PER_HOUR;
1479         int minutes = (int) ((effectiveTotalSecs % SECONDS_PER_HOUR) / SECONDS_PER_MINUTE);
1480         int secs = (int) (effectiveTotalSecs % SECONDS_PER_MINUTE);
1481         StringBuilder buf = new StringBuilder(24);
1482         buf.append("PT");
1483         if (hours != 0) {
1484             buf.append(hours).append('H');
1485         }
1486         if (minutes != 0) {
1487             buf.append(minutes).append('M');
1488         }
1489         if (secs == 0 && nanos == 0 && buf.length() > 2) {
1490             return buf.toString();
1491         }
1492         if (seconds < 0 && nanos > 0) {
1493             if (secs == 0) {
1494                 buf.append("-0");
1495             } else {
1496                 buf.append(secs);
1497             }
1498         } else {
1499             buf.append(secs);
1500         }
1501         if (nanos > 0) {
1502             int pos = buf.length();
1503             if (seconds < 0) {
1504                 buf.append(2 * NANOS_PER_SECOND - nanos);
1505             } else {
1506                 buf.append(nanos + NANOS_PER_SECOND);
1507             }
1508             while (buf.charAt(buf.length() - 1) == '0') {
1509                 buf.setLength(buf.length() - 1);
1510             }
1511             buf.setCharAt(pos, '.');
1512         }
1513         buf.append('S');
1514         return buf.toString();
1515     }
1516 
1517     //-----------------------------------------------------------------------
1518     /**
1519      * Writes the object using a
1520      * <a href="../../serialized-form.html#java.time.Ser">dedicated serialized form</a>.
1521      * @serialData
1522      * <pre>
1523      *  out.writeByte(1);  // identifies a Duration
1524      *  out.writeLong(seconds);
1525      *  out.writeInt(nanos);
1526      * </pre>
1527      *
1528      * @return the instance of {@code Ser}, not null
1529      */
1530     private Object writeReplace() {
1531         return new Ser(Ser.DURATION_TYPE, this);
1532     }
1533 
1534     /**
1535      * Defend against malicious streams.
1536      *
1537      * @param s the stream to read
1538      * @throws InvalidObjectException always
1539      */
1540     private void readObject(ObjectInputStream s) throws InvalidObjectException {
1541         throw new InvalidObjectException("Deserialization via serialization delegate");
1542     }
1543 
1544     void writeExternal(DataOutput out) throws IOException {
1545         out.writeLong(seconds);
1546         out.writeInt(nanos);
1547     }
1548 
1549     static Duration readExternal(DataInput in) throws IOException {
1550         long seconds = in.readLong();
1551         int nanos = in.readInt();
1552         return Duration.ofSeconds(seconds, nanos);
1553     }
1554 
1555 }